Positionable adhesives are those that allow for the placement of an article containing such an adhesive onto a receptor in an exact position, because the article can be adjusted relative to the receptor after initial placement.
In some instances, the adhesive can be designated repositionable or repeatedly reusable. As used herein, the term "repositionable" refers to the ability to be repeatedly adhered to and removed from a substrate without substantial loss of adhesion capability. Such adhesives exhibit aggressive tack but low peel adhesion properties, thus allowing repeated reusability. Commercial products such as the 3M brand Post-It.TM. Notes display such adhesive characteristics.
Solid, inherently tacky, elastomeric microspheres are known in the art to be useful in repositionable adhesive applications. Microsphere-based adhesives are thought to perform well in such applications at least in part due to their "self-cleaning" nature wherein substrate contaminants tend to be pushed aside and trapped between the microspheres as the adhesive is applied. Upon removal, the adhesive still presents a relatively uncontaminated surface for reapplication to the substrate.
One problem associated with these types of adhesives has been microsphere transfer, i.e., microsphere loss to a receptor. That is, microsphere loss from a substrate on which the microsphere has been positioned to a surface to which the substrate has been adhered by the microsphere. To alleviate this problem, binders or primers have been utilized.